6,197 research outputs found
Simulation of the CMS Resistive Plate Chambers
The Resistive Plate Chamber (RPC) muon subsystem contributes significantly to
the formation of the trigger decision and reconstruction of the muon trajectory
parameters. Simulation of the RPC response is a crucial part of the entire CMS
Monte Carlo software and directly influences the final physical results. An
algorithm based on the parametrization of RPC efficiency, noise, cluster size
and timing for every strip has been developed. Experimental data obtained from
cosmic and proton-proton collisions at TeV have been used for
determination of the parameters. A dedicated validation procedure has been
developed. A good agreement between the simulated and experimental data has
been achieved.Comment: to be published in JINS
Omega and Antiomega production in central Pb+Pb collisions at 40 and 158 AGeV
Results are presented on Omega production in central Pb+Pb collisions at 40
and 158 AGeV beam energy. Given are transverse-mass spectra, rapidity
distributions, and total yields for the sum Omega+Antiomega at 40 AGeV and for
Omega and Antiomega separately at 158 AGeV. The yields are strongly
under-predicted by the string-hadronic UrQMD model and are in better agreement
with predictions from a hadron gas models.Comment: 5 papes, 4 figures, 1 table, updated figure 4 and table 1. Final
version, including some editorial changes, as published in PR
Report from NA49
The most recent data of NA49 on hadron production in nuclear collisions at
CERN SPS energies are presented. Anomalies in the energy dependence of pion and
kaon production in central Pb+Pb collisions are observed. They suggest that the
onset of deconfinement is located at about 30 AGeV. Large multiplicity and
transverse momentum fluctuations are measured for collisions of intermediate
mass systems at 158 AGeV. The need for a new experimental programme at the CERN
SPS is underlined.Comment: invited talk presented at Quark Matter 2004, 10 page
Electric charge fluctuations in central Pb+Pb collisions at 20, 30, 40, 80 and 158 AGeV
Results are presented on event-by-event electric charge fluctuations in
central Pb+Pb collisions at 20, 30, 40, 80 and 158 AGeV. The observed
fluctuations are close to those expected for a gas of pions correlated by
global charge conservation only. These fluctuations are considerably larger
than those calculated for an ideal gas of deconfined quarks and gluons. The
present measurements do not necessarily exclude reduced fluctuations from a
quark-gluon plasma because these might be masked by contributions from
resonance decays.Comment: 19 pages, 8 figure
Observation of an Exotic S = -2, Q = -2 Baryon Resonance in Proton-Proton Collisions at the CERN SPS
Results of resonance searches in the Xi- pi-, Xi- pi+, antiXi+ pi- and
antiXi+ pi+ invariant mass spectra in proton-proton collisions at sqrt{s}=17.2
GeV are presented. Evidence is shown for the existence of a narrow Xi- pi-
baryon resonance with mass of 1.862+/-0.002 GeV/c^2 and width below the
detector resolution of about 0.018 GeV/c^2. The significance is estimated to be
4.0 sigma. This state is a candidate for the hypothetical exotic Xi_(3/2)^--
baryon with S = -2, I = 3/2 and a quark content of (d s d s ubar). At the same
mass a peak is observed in the Xi- pi+ spectrum which is a candidate for the
Xi_(3/2)^0 member of this isospin quartet with a quark content of (d s u s
dbar). The corresponding antibaryon spectra also show enhancements at the same
invariant mass.Comment: 5 pages, 3 figure
Rapidity and energy dependence of the electric charge correlations in A+A collisions at the SPS energies
Results from electric charge correlations studied with the Balance Function
method in A+A collisions from 20\emph{A} to 158\emph{A} GeV are presented in
two different rapidity intervals: In the mid-rapidity region we observe a
decrease of the width of the Balance Function distribution with increasing
centrality of the collision, whereas this effect vanishes in the forward
rapidity region.
Results from the energy dependence study in central Pb+Pb collisions show
that the narrowing of the Balance Function expressed by the normalised width
parameter \textit{W} increases with energy towards the highest SPS and RHIC
energies.
Finally we compare our experimental data points with predictions of several
models. The hadronic string models UrQMD and HIJING do not reproduce the
observed narrowing of the Balance Function. However, AMPT which contains a
quark-parton transport phase before hadronization can reproduce the narrowing
of the BF's width with centrality. This confirms the proposed sensitivity of
the Balance Function analysis to the time of hadronization.Comment: Submitted in Phys. Rev.
Measurement of the Ratio Gamma(KL -> pi+ pi-)/Gamma(KL -> pi e nu) and Extraction of the CP Violation Parameter |eta+-|
We present a measurement of the ratio of the decay rates Gamma(KL -> pi+
pi-)/Gamma(KL -> pi e nu), denoted as Gamma(K2pi)/Gamma(Ke3). The analysis is
based on data taken during a dedicated run in 1999 by the NA48 experiment at
the CERN SPS. Using a sample of 47000 K2pi and five million Ke3 decays, we find
Gamma(K2pi)/Gamma(Ke3) = (4.835 +- 0.022(stat) +- 0.016(syst)) x 10^-3. From
this we derive the branching ratio of the CP violating decay KL -> pi+ pi- and
the CP violation parameter |eta+-|. Excluding the CP conserving direct photon
emission component KL -> pi+ pi- gamma, we obtain the results BR(KL -> pi+ pi-)
= (1.941 +- 0.019) x 10^-3 and |eta+-| = (2.223 +- 0.012) x 10^-3.Comment: 20 pages, 7 figures, accepted by Phys. Lett.
System-size dependence of strangeness production in nucleus-nucleus collisions at sqrt{s_{NN}}=17.3 GeV
Emission of pi, K, phi and Lambda was measured in near-central C+C and Si+Si
collisions at 158 AGeV beam energy. Together with earlier data for p+p, S+S and
Pb+Pb, the system-size dependence of relative strangeness production in
nucleus-nucleus collisions is obtained. Its fast rise and the saturation
observed at about 60 participating nucleons can be understood as onset of the
formation of coherent partonic subsystems of increasing size.Comment: Phys.Rev.Lett in print; version2: changes made according to the
request of the referee
Inclusive production of charged pions in p+C collisions at 158 GeV/c beam momentum
The production of charged pions in minimum bias p+C interactions is studied
using a sample of 377000 inelastic events obtained with the NA49 detector at
the CERN SPS at 158 GeV/c beam momentum. The data cover a phase space area
ranging from 0 to 1.8 GeV/c in transverse momentum and from -0.1 to 0.5 in
Feynman x. Inclusive invariant cross sections are given on a grid of 270 bins
per charge thus offering for the first time a dense coverage of the projectile
hemisphere and of the cross-over region into the target fragmentation zone.Comment: 31 pages, 30 figures, submitted to European Journal of Physic
Measurement of the branching ratio of the decay
From the 2002 data taking with a neutral kaon beam extracted from the
CERN-SPS, the NA48/1 experiment observed 97 candidates with a background contamination of events.
From this sample, the BR() is measured to be
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